* Distribute-lists used to filter routes from routing updates are applied under the interface with the <b>ip distribute-list eigrp</b> command, as opposed to under the EIGRP router instance.

* Distribute-lists used to filter routes from routing updates are applied under the interface with the <b>ip distribute-list eigrp</b> command, as opposed to under the EIGRP router instance.

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* Maximum prefix thresholds (warning and withdraw) can be configured for redistributed routes using the <b>redistribute maximum-prefix</b> routing process command. Cisco IOS Software does not have the ability to set maximum prefix thresholds for redistributed routes.

+

* Maximum prefix thresholds (warning and withdraw) can be configured for redistributed routes using the <b>redistribute maximum-prefix</b> routing instance command. Cisco IOS Software does not have the ability to set maximum prefix thresholds for redistributed routes.

* A route-map is always required when redistributing routes into an EIGRP instance. In Cisco IOS Software, a route-map is optional.

* A route-map is always required when redistributing routes into an EIGRP instance. In Cisco IOS Software, a route-map is optional.

Revision as of 04:01, 11 January 2011

Objective

This tech note outlines the main differences in Enhanced Interior Gateway Protocol (EIGRP) support between Cisco® NX-OS Software and Cisco IOS® Software. Sample configurations are included for Cisco NX-OS and Cisco IOS Software for some common features to demonstrate the similarities and differences. Please refer to the NX-OS documentation on Cisco.com for a complete list of supported features.

EIGRP Overview

EIGRP is a Cisco proprietary hybrid distance vector routing protocol used to exchange network reachability information within an autonomous system.

Important Cisco NX-OS and Cisco IOS Software Differences

In Cisco NX-OS:

The EIGRP protocol supports In-Service-Software-Upgrades (ISSU) if two supervisors are present in a chassis (Graceful Restart must be enabled).

EIGRP command-line interface (CLI) configuration and verification commands are not available until you enable the EIGRP feature with the feature eigrp command.

Eight equal-cost paths are supported by default; Cisco NX-OS supports up to 16.

Route auto-summarization is disabled by default.

Networks and interfaces are added to an EIGRP instance under the interface configuration mode.

If a router ID is not manually configured, the loopback 0 IP address is always preferred. If loopback 0 does not exist, Cisco NX-OS selects the IP address for the first loopback interface in the configuration. If no loopback interfaces exist, Cisco NX-OS selects the IP address for the first physical interface in the configuration.

A default route can be generated with the default-information originate command, whereas Cisco IOS Software requires additional CLI commands to achieve similar results.

When interface authentication is configured, the EIGRP key is encrypted with Data Encryption Standard 3 (3DES) in the configuration. Cisco IOS Software requires the service password command.

Distribute-lists used to filter routes from routing updates are applied under the interface with the ip distribute-list eigrp command, as opposed to under the EIGRP router instance.

Maximum prefix thresholds (warning and withdraw) can be configured for redistributed routes using the redistribute maximum-prefix routing instance command. Cisco IOS Software does not have the ability to set maximum prefix thresholds for redistributed routes.

A route-map is always required when redistributing routes into an EIGRP instance. In Cisco IOS Software, a route-map is optional.

Things You Should Know

The following list provides some additional facts about Cisco NX-OS that should be helpful when designing, configuring, and maintaining an EIGRP network.

Four EIGRP instances can be configured per virtual device context (VDC).

Numerous Virtual Route Forwarding (VRF) instances can be associated with an EIGRP instance.

If the feature eigrp command is removed, all relevant EIGRP configuration information is also removed.

The shutdown command can be used to gracefully disable an EIGRP instance while retaining the configuration. This feature can also be applied per interface with the ip eigrp <instance> shutdown command.

The show running-config eigrp command displays the current EIGRP configuration.

An EIGRP instance can be restarted with the restart eigrp <instance> Exec command.

Graceful restart (RFC 3623) is enabled by default (It needs to be enabled in order to perform an ISSU upgrade.)

Multiple EIGRP instances can be configured on the same interface.

Secondary IP addresses are advertised by default and cannot be suppressed per interface.

EIGRP supports Bidirectional Forwarding Detection (BFD) to reduce network convergence time to less than one second.

Configuration Comparison

The following sample code shows configuration similarities and differences between the Cisco NX-OS and Cisco IOS Software CLIs. There are three significant differences: Cisco NX-OS allows EIGRP to be enabled and disabled globally, and it has a more interface-centric configuration that makes it easier to read. In addition, Cisco NX-OS has the capability to generate a default route, whereas Cisco IOS Software requires additional CLI commands to achieve similar results.

Cisco IOS CLI

Cisco NX-OS CLI

Enabling the EIGRP Feature

Cisco IOS Software does not have the ability to enable or disable EIGRP.